Rather than roaming a noisy and distraction-laden environment, subjects are thus often seated in front of a computer monitor, focusing their attention on a very deliberately constructed set of stimuli, performing a task for which they may have received special training or instruction. They are, in a sense, passive recipients of stimulation that has been especially designed to elicit information about cognitive algorithms located exclusively in their brains

The question that vision theory addresses is this: how does stimulation on the retina become a perception of the world? Cognitive scientists also emphasize the apparent fact that the patterns of stimulation on the retina do not carry enough information on their own to determine a unique visual perception. The visual system must therefore embellish visual inputs, make assumptions, and draw inferences in order to yield a correct solution—an accurate description of the visual scene

The conditions for being a symbol do not, apparently, mandate that symbols be made of any particular stuff, but instead focus on functional criteria, on criteria about what symbols must do. Among the relevant conditions seem to be these. First, symbols can “stand for” or represent things.